1. Field of the Invention
This invention relates to a universal semiconductor cell capable of being configured as an NPN transistor, a PNP transistor, a diode or a resistive element and to integrated circuits using one or more of these universal cells.
2. Description of the Prior Art
Semiconductor products are typically classified as standard products (i.e., products designed for general application and available off the shelf from distributors or manufacturers) and custom products (i.e., products uniquely designed for a particular application and customer and available only to that customer). However, a class of intermediate-type products using a standard silicon substrate manufactured in large volume but capable of being configured to suit the particular needs of a customer has been developed to give some of the advantages of high volume production to custom products generally used in quantities less than the high volume required for standard products. A typical product of this type is a gate array. A gate array is fabricated by placing on a base array (manufactured in high volume so as to achieve the economies of large volume production) a unique metallization layer configured to meet the needs of the particular customer, thereby to provide a circuit uniquely suitable for a particular application. A gate array is one example of an application specific integrated circuit (sometimes called an "ASIC"). Typically, ASIC's are used in digital logic where the logic circuit is configured to meet a particular customer's needs by changing the metallization pattern or patterns formed on the standard base array.
While ASIC technology has been commonplace in digital logic, to date linear circuits have not been as easy to implement as ASIC's because linear circuits are generally custom designed for their particular applications. While numerous linear circuits are manufactured as standard products, these circuits are still restricted to particular uses contemplated at the time of their design. Accordingly, there is a need for a linear circuit which is capable of being configured for specific uses which can be manufactured as a standard product in large quantities to achieve the economies of large scale production but which is capable of being configured as a custom product for a particular design.